Unit 12 - Misc. Topics Flashcards
most effective single method of perioperative warming
forced air warmer
afferent limb of temperature regulation
thermoreceptors
- skin
- deep tissue
- spinal cord
control center of temperature regulation
- hypothalamus (preoptic region)
- brainstem
efferent responses to hypothermia
- vasoconstriction
- piloerection
- shivering
- nonshivering thermogenesis
efferent response to hyperthermia
- vasodilation
- diaphoresis
4 mechanisms of heat transfer
- radiation
- convection
- evaporation
- conduction
how does a patient lose heat via infrared radiation
if the patient is warmer than the environment, then heat is lost to the environment
what type of heat transfer does covering the patient reduce
radiant
number 2 source of heat loss
convection
what is convection?
what % of periop heat transfer does it account for?
transfer of heat by movement of matter
15-30%
how is heat lost via convection?
air movement over the body whisks away heat that has radiated from the body
the body radiates more heat to replace what was taken away by airflow
how does laminar flow affect the amount of heat lost to convection
increases
amount of energy to vaporize water
latent heat of vaporization
what % of heat transfer does evaporation account for in the periop pt
20%
how can water be lost by evaporation during surgey?
- respirations
- wounds
- internal organ exposure
the rate of this process is a function of the exposed surface area and the relative humidity of the environment
evaporation
what is conduction?
what % of heat transfer does this account for in periop pt?
heat is lost when the patient comes into direct contact with a cooler object
< 5%
examples of heat loss through conduction
- cold OR table
- cold IV fluids
- cold irrigation fluids
the amount of conductive heat loss is a function of:
the temperature gradient and thermal conductivity of the object
phase 1 of intraoperative heat transfer
how long does this phace last?
heat redistribution from core to periphery
first hour after induction of anesthesia
what is phase 2 of intraoperative heat transfer?
when does this occur?
heat transfer is greater than heat production
hours 1-5 after induction
what is phase 3 of intraoperative heat transfer?
when does this occur?
equilibrium develops between heat lost to environment and heat production
hours 5-7 after induction
what causes heat redistribution during general, spinal, or epidural anesthesia?
redistribution of heat from central compartment to peripheral compartment
perioperative events contributing to heat loss
- recalibration of the hypothalamic set point
- drug induced vasodilation
- impaired shivering
- core to peripheral temperature redistribution
- cool ambient temp
- cold OR table
- admin of room temp fluids and cold blood products
what is the most significant source of heat loss in the OR?
radiation
what is the least significant source of heat loss in the OR?
conduction
a heat lamp is an example of what type of heat transfer
radiation
what temp monitoring site offers the best combination of accuracy and safety over an extended period of time
esophageal
CV consequences of periop hypothermia
- SNS stimulation
- vasoconstriction, decreased tissue PaO2
- coagulopathy, plt dysfunction
- hgb S sickling
- oxyhgb dissociation curve shifts to the left
how does hypothermia affect the oxyhgb dissociation curve
shifts to the left
pharmacologic consequences of hypothermia
- slowed drug metabolism
- increased solubility of volatiles
how does shivering increase the risk of myocardial ischemia and infarction
increases O2 consumption by 400-500%
pharmacologic modalities used to treat postop shivering
- meperidine
- clonidine
- dexmedetomidine
how does hypothermia affect O2 consumption?
reduces by 5-7% for every 1 degree C reduction in body temp
when might induced hypothermia be useful?
- cerebral ischemia (stroke)
- cerebral aneurysm clipping
- TBI
- bypass
- cardiac arrest
- aortic cross clamping
- CEA
what type of temperature monitoring site reflects temp of vital organs?
core body temp
ideal position of esophageal temp probe
distal 1/3 to 1/4th of esophagus
placement of adult esophageal temp probe
38-42cm past incisors
placement of esophageal temp probe in an adult with a 2nd generation SGA
15-20 cm distal to drain tube
pediatric placement of esophageal temp probe
10 + (2x age in yrs) / 3 cm past incisors
why is esophageal temp increased if placed in stomach
due to heat created by liver metabolism
why may temp be decreased if esophageal temp probe is placed in proximal esophagus
- cool inspiratory gas
- continuous gastric suction
- thoracotomy
ideal position of nasopharyngeal temp prob and why
sensor contacts posterior nasopharyngeal wall posterior to soft palate
close to hypothalamus
what causes decreased temp reading of nasopharyngeal temp probe
leakage of inspiratory gas
ideal position of rectal temp probe
8 cm in adults, 3 cm in children
what causes temp reading of rectal temp probe to be increased or decreased
- increased: heat producing bacteria in the gut
- decreaesd: cool blood from lower extremities, stool
temperature measurement sites that lag during rapid warming and cooling
- rectal
- bladder
what causes bladder temp to read low?
inadequate UOP
when is temp reading via pulmonary artery not reliable?
- CBP
- thoracotomy
skin temp is often ___ deg C less than core temp
2-4
how can skin temp be used to assess onset of a regional block?
temp will rise if the block is good d/t sympathectomy-induced rise in peripheral blood flow
5 clinically relevant CV consequences of perioperative hypothermia
- myocardial ischemia/arrythmias
- decreased DO2
- surgical site infection
- increased blood loss (coagulopathy)
- risk of sickle cell crisis in pts with SCD
why should saline be added to the ETT cuff vs. air for removal of vocal cord papilloma with laser
- acts as a heat sink for thermal energy produced by the laser
- if laser breaks the balloon, surgeon will see saline in surgical field (more obvious if dyed)
eye protection needed when CO2 laser is used
clear lenses
3 ingredients to produce a fire
(components of fire triangle)
- ignition source (cautery, laser)
- fuel (ETT, drapes, surgical supplies)
- oxidizer (O2, N2O)
5 steps to take when fire is present in the OR
- stop ventilation, remove ETT
- stop flow of all airway gases
- remove other flammable material from airway
- pour water or saline into airway
- if fire isn’t extinguished on 1st attempt, use a CO2 fire extinguisher
3 steps to take after OR fire is controlled
- re-establish ventilation via mask. avoid supplemental O2 or N2O
- check ETT for damage - fragments may be in pt’s airway
- perform bronch to inspect for retained fragments
what is LASER an acronym for
Light Amplification by Stimulated Emission of Radiation
3 things that make laser light different from ordinary light
it is
1. monochromatic (light is a single wavelength)
2. coherent (light oscillates in same phase)
3. collimated (light exists as a narrow parallel beam)
which absorbs more water - long wavelength lasers or short?
long
which lasers penetrate deeper into tissue - long or short wavelength?
short
wavelength of CO2 lasers
10,600 nm
type of laser used in oropharyngeal and vocal cord surgeries
CO2
structure damaged by CO2 lasers
cornea
wavelength of Nd:YAG lasers
1064 nm
type of lasers used for tumor debulking and tracheal surgeries
Nd:YAG
structure damaged by Nd:YAG lasers
retina
eye protection for Nd:YAG lasers
green goggles
(Nd:YAG=Green)
wavelength of ruby lasers
694 nm
type of laser used for retinal surgery
ruby
structure damaged by ruby laser
retina
eye protection for ruby lasers
red goggles
(Ruby = Red)
wavelength of argon lasers
515 nm
type of surgery argon lasers are used for
vascular lesions
structure damaged by argon laser
retina
eye protection for Argon lasers
Amber goggles
(Argon = Amber)
which component of the ETT is the most vulnerable to lasers
cuff
T/F - laser resistant tubes have laser resistant cuffs
false
why do laser resistant ETTs have 2 cuffs
the proximal cuff is filled with saline/dye. if it is perforated by laser, the distal cuff will hopefully remain intact and permit continued PPV
what should determine the choice of ETT in laser surgeries
type of laser and its wavelength
which ETT is a good choice for CO2 laser use
LaserFlex
which ETT is a good choice for Nd:YAG laser
Lasertubus
techniques that do not require an ETT (removing 1 component of fire triangle)
- spontaneous ventilation
- intermittent PPV via facemask and apnea
- jet ventilation
why is gas embolus a risk of laser surgery?
gas may be used to cool the tip of the laser probe
T/F - laser resistant ETTs reduce the risk of fire when ESU cautery is used
false
how to protect pt’s eyes in laser surgery
- tape eyes closed
- avoid petroleum-based lubricants
- cover eyelids with saline-soaked gauze
- use protective glasses
best ways to protect yourself against laser plume
- smoke evacuator
- high-efficiency masks
what creates a plume of fine particulates with lasers?
tissue vaporization
rule of nines (adult)
head = 10%
trunk = 36%
arm = 9%
leg = 18%
perineum = 1%
involvement of a 1st degree burn
epidermis only
involvement of a 2nd degree burn
superficial: epidermis to upper dermis
deep: epidermis to lower dermis
involvement of 3rd degree burn (full thickness burn)
subcutaneous tissue
complete destruction of epidermis and dermis
involvement of a 4th degree (full thickness) burn
extends to muscle and bone
what burn stages have no sensation d/t obliterated nerve endings
3rd & 4th degree
rule of nines (child)
head = 19% (9.5% per front/back)
trunk = 16% (each side)
leg = 15%
arm = 9.5%
palm (excluding fingers) = 1%
general rule for rule of nines and head surface area in children
for every year > 1 year up to 10 years, you can decrease the head surface area by 1% and increase each leg by 0.5%
best IV fluid to give in initial 24 hours after major burn
LR
why should albumin be avoided in the first 24 hours after a major burn?
lost to interstitial space
what creates a capillary leak immediately after a burn?
increased microvascular permeability
what consequences of capillary leak after burn injury result in edema formation
- increased vascular permeability
- loss of protein-rich fluid to interstitial space, decreased plasma oncotic pressure
what are fluid requirements in the first 24 hours following a burn?
fluid shifts and edema formation are the greatest in the first 12 hours and begin to stabilize by 24 hours
what lab value sugests inadequate volume resuscitation in the first few days of a burn
rising hgb
when to consider transfusion in burn pt
Hct < 20 (healthy pt)
Hct < 30 (pre-existing CV disease)
Parkland formula
first 24 hours:
- 4 mL LR x % TBSA burned x kg
- give 1/2 in first 8 hours
- 1/2 in next 16 hours
second 24 hours:
- D5W mainenance rate
- 0.5 mL colloid x % TBSA x kg
Modified Brooke Formula
first 24 hours:
- 2 mL LR x % TBSA x kg
- 1/2 in first 8 hours
- 1/2 in next 16 hours
second 24 hours:
- D5W MIVF
- 0.5 mL colloid x % TBSA burned x kg
clinical end points of burn resuscitation - UOP
adult: > 0.5 mL/kg/hr
child (<30 kg): > 1 mL/kg/hr
high voltage electrical injury: > 1-1.5 mL/kg/hr (myoglobin is nephrotoxic)
clinical end points of burn resuscitation: blood pressure
adult: MAP > 60
infant: SBP > 60
child: SBP 70-90 + (2 x age in yrs)
clinical end points of burn resuscitation: base deficit
< 2
clinical end points of burn resuscitation: oxygen delivery index
600 mL O2/min/m2
clinical end point of burn resuscitation: mixed venous oxygen tension (PvO2)
35-45 mmHg
why is it important to maintain a higher UOP with electrical burns
myoglobinemia is caused by extensive muscle damage - myoglobin is nephrotoxic
what defines abdominal compartment syndrome
IAP > 20 mmHg + evidence of organ dysfunction (HD instability, oliguria, increased PIP)
treatment of abd compartment syndrome
- neuromuscular blockade
- sedation
- diruesis
- abdominal decompression vs. laparotomy
CO binds to hgb with an affinity of ____x that of O2
200
how does carbon monoxide
affect the oxyhgb dissociation curve
shifts to the left, impairs offloading of O2 to tissues
(left = love)
acid-base abnormality seen in CO poisoning
metabolic acidosis (inadequate O2 delivery and utilization)
why is the pulse ox not accurate in CO poisoning?
it’s unable to distinguish between HgbO2 and HgbCO
may be falsely elevated
treatment of CO poisoning
100% O2
hyperbaric oxygen
first priority in treatment of all burn pts
high FiO2
gold standard for diagnosing extent of airway inujry in burns
fiberoptic bronch
why should a surgical airway only be used as a last resort in burn pts
increases risk of pulmonary sepsis and late pulmonary complicaitons
when does upregulation of extrajunctional receptors begin in burn pts
what is the significance of this?
after 24 hours
succs is safe within first 24 hours after burn - use after 24 hours can cause lethal hyperkalemia
dosing nondepolarizing NMBs in burn pts
increase 2-3 fold (more receptors)
mechanisms of heat loss in a burn pt
- 60% radiation
- 25% evaporation
- 12% convection
- 3% conduction
*normal heat loss: radiation 60%, convection 15-20%, evaporation 20%, conduction < 5%
metabolic changes in burn pts
hypermetabolic
- increased catabolism
- increased O2 consumption
- increased HR
- increased RR
ANS activity during ECT
initial response: increased PNS activity during tonic phase (~15 seconds)
secondary response: increased SNS activity during clonic phase (lasts several minutes)
how does LIthium affect NMBs
prolongs succs and NDNMBs
neuro effects of the clonic phase of ECT-induced seizures
- increased ICP
- increased CBF
- increased IOP
absolute contraindications to ECT
- recent MI ( <4-6 months)
- recent intracranial surgery ( <3 months)
- recent stroke (<3 months)
- brain tumor
- unstable c spine
- pheochromocytoma
relative contraindications to ECT
- pregnancy
- pacemaker/ICD
- CHF
- glaucoma
- retinal detachment
- severe pulmonary disease
minimum recommended seizure duration for ECT
25 seconds
drugs that increase seizure duration
- etomidate
- ketamine
- alfentanil with propofol
- aminophylline
- caffeine
drugs that decrease seizure duration
- propofol
- versed
- ativan
- fentanyl
- lidocaine
gold standard anesthetic for ECTs. why?
methohexital - rapid recovery, no effect on sz duration
negative side effects of etomidate for ECTs
- myoclonus
- increased PONV
- more HTN
negative effects of ketamine for ECT
- increased SNS response
- prolonged recovery
why is glycopyrrolate used for ECTs
- antisialagogue
- reduced bradycardia/asystole
use of esmolol in ECTs
blunts SNS response
how do hyper and hypoventilation impact seizure duration with ECT
hypo: decreased
hyper: increased
interaction between MAOIs and indirect acting sympathomimetics
HTN crisis
are oral and gastric secretions increased during the initial or secondary response to ECT
initial
how does lidocaine affect sz duration in ECTs
decreased sz activity
does esmolol affect sz activity in ECTs?
nope
how does clonidine affect sz activity in ECTs
doesn’t
cause of neuroleptic malignant syndrome
what is the antidote?
dopamine depletion in basal ganglia and hypothalamus
bromocriptine (restores dopamine concentrations in these regions)
cause of serotonin syndrome
what is the antidote
excess 5-HT activity in CNS and PNS
cyproheptadine (5-HT antagonist)
antitode for anticholinergic poisoning
physosigmine (only cholinesterase inhibitor that lacks quarternay ammonium and diffuses into CNS to increase ACh concentration)
key features of malignant hyperthermia
- hypercarbia
- tachycardia
- myoglobinemia
- acidosis
- muscle rigidity
symptoms that NMS and MH have in common
- muscle rigidity
- hyperthermia
- tachycardia
- acidosis
drug used to treat both NMS and MH
dantrolene
what drugs increase risk of serotonin syndrome when combined with SSRIs
fentanyl, meperidine
what drugs increase risk of serotonin syndrome when combined with MAOIs
meperidine, ephedrine
what drugs increase risk of serotonin syndrome when combined with methylene blue
other serotonergic drugs
intraocular perfusion pressure =
MAP - IOP
how long is N2O contraindicated for after an intraocular SF6 bubble is placed
10 days after
main blood supply to the eye
where does it branch off?
opthalmic artery
branches off internal carotid near circle of Willis
what transports venous blood to the cavernous sinus?
superior and inferior opthalamic veins
what is the main blood supply to the eye
opthalamic artery
what 3 components determine IOP
- chorodial blood volume
- aqueous fluid volume
- extraocular muscle tone
what is normal IOP
10-20 mmHg
what produces aqueous humor?
where is aqueous humor reabsorbed?
produced by ciliary process
reabsorbed by Canal of Schlemm
intraoperative events that increase IOP
- hypercarbia
- hypoxemia
- increased CVP
- increased MAP
- DL
- straining/coughing
- succinylcholine
- N2O (if SF6 bubble in place)
- Trendelenberg
- Prone
- external compression by facemask
intraoperative events that decrease IOP
- hypocarbia
- decreased CVP
- decreased MAP
anesthetic agents that decrease IOP
- volatiles
- N2O
- NDNMBs
- propofol
- opioids
- benzos
- hypothermia
do anticholinergics increase IOP
nope
how does LMA placement vs DL effect IOP
LMA: minimal
DL: increased
how does succinylcholine affect IOP
increases by 5-10 mmHg for up to 10 min
*not reliably blocked by defasciculating NMB
what NMB should be used in an open globe injury
full stomach/difficult airway - succs
otherwise - roc
dose of rocuronium for an open globe injury
1.2 mg/kg (RSI dose)
drugs that decrease aqueous humor production
- acetazolamide (inhibits carbonic anhydrase)
- timolol (nonselective beta agonist)
2 ways drugs can decrease IOP
- decrease aqueous humor production
- facilitate aqueous humor drainage
drug that facilitates aqeous humor drainage
anesthetic implications of this drug
echothiophate (irreversible cholinesterase inhibitor)
can prolong duration of succs and ester type LAs
2 key considerations for strabismus surgery
- incrased risk PONV
- increased risk of activating oculocardiac reflex
nerves that make up oculocardiac reflex
CN V (afferent)
CN X (efferent)
N2O considerations for eye surgery
if a sulfur hexafluoride bubble (SF6) is placed, N2O can expand the bubble and cause blindness
d/c 15 min before bubble placed
avoid for 7-10 days after bubble placed
SF6 alternatives and times to avoid N2O
silicone oil = 0 days
air bubble = 5 days
perfluopropane (C3F8) = 30 days
what causes open angle glaucoma
sclerosis of trabecular meshwork; impairs aqueous humor drainage
procedures TAP block is best suited for
abdominal procedures involving T9-L1 distribution (general, GYN, urologic)
abdominal wall structures from superficial to deep
- sub q tissue
- external oblique
- internal oblique
- transverse abdominis
- peritoneum
where does innervation of the anterolateral abdominal wall arise from?
how are these nerves blocked?
T7-L1
blocked by placing LA below fascial plane between IO and TA
where is US placed for TAP block
a few cm superior and parallel to iliac crest
2 pops felt during blind technique for TAP block
- after needle transverses EO
- after needle transverses IO
volume of LA injected for TAP block
15-20 mL per side
complications of TAP block
- peritoneal puncture
- liver hematoma
what is a TAP block?
unilateral peripheral nerve block that targets nerves of anterior and lateral abdominal wall
what 3 landmarks form the triangle of Petit?
- EO
- latissimus dorsi
- iliac crest
where should LA be injected when placing a TAP block?
in fascial plane between IO and TA muscles
algogenic
stimulus that is expected to produce pain
pain due to a stimulus that doesn’t normally produce pain is called:
allodynia
exaggerated pain response to a painful stimulus is called:
hyperalgesia
pain localized to a dermatome is called:
neuralgia
(ex. burning sensation from diabetic neuropathy) is called:
dysesthesia
paresthesia
abnormal sensation described as pins and needles
inhibitory neurotransmitters used by the descending inhibitory pain pathway
norepinephrine
serotonin
antidepressants that can be used to treat chronic pain
TCAs
SSRIs
SNRIs
CV side effects of TCAs
- prolonged QT
- orthostatic hypotension
what characterizes complex regional pain syndrome
neuropathic pain with autonomic involvement
risk factors for complex regional pain syndrome
- female
- previous trauma
- previous surgery
key distinction between type 1 and type 2 complex regional pain syndrome
type 2 always preceded by nerve injury; type 1 is not
treatments for complex regional pain syndrome
- ketamine
- memantine (NMDA antagonist)
- gabapentin
- regional sympathetic blockade
- PT
- steroids
- amitriptyline
what is a thoracic paravertebral block
LA injected into paravertebral space to target ventral ramus of spinal nerve as it exits vertebral foramen
what does a thoracic paravertebral block cover
unilateral sensory and sympathetic block along that specific dermatome
how many dermatomes are covered by a thoracic paravertebral block?
one - the level injected
what types of surgeries see pain relief with a thoracic paravertebral block
- breast
- thoracotomy
- rib fracture
block useful for cancer pain of upper abdominal organs
celiac plexus block
complications of a celiac plexus block
- orthostatic hypotension
- retroperitoneal hematoma
- hematuria
- diarrhea
- AAA dissection
- back pain
- retrograde migration of injectate
nerve block useful in management of cancer pain of pelvic organs
superior hypogastric plexus block
complications of hypogastric plexus block
retrograde migration of injectate
use of a sphenopalatine block
relieve postdural puncture headache
only cranial nerve that is part of the CNS
optic nerve
complication of retrobulbar block causing blindness (contralateral amaurosis)
LA injected into optic sheath (can migrate toward optic chiasm and anesthetize CN II & III on the side opposite the block)
what is post-retrobulbar block apnea syndrome
when is it usually evident?
LA that reaches the brainstem and causes apnea
2-5 min after injection
when does spontaneous ventilation normally return after post-retrobulbar block apnea syndrome
in 15-20 minutes
when should you anticipate development of post-retrobulbar block syndrome?
assess contralateral pupil - if pupil starts small but dilates shortly after the block, anticipate apnea syndrome
risks assoc. with aminoglycosides
examples of aminoglycosides
- ototoxicity, nephrotoxicity, skeletal muscle weakness
- gentamycin, streptomycin
adverse effects of tetracyclines
- hepatotoxicity
- nephrotoxicity
AEs of fluoroquinololes
examples of fluoroquinolones
- Gi intolerance, tendonitis, tendon rupture
- ciproflaxin, levofloxacin, moxifloxacin
anesthetic implcation of macrolides
CYP450 inhibition
antibiotics that cause skeletal muscle weakness
- aminoglycosides
- clindamycin
why is hypotension associated with vancomycin admin?
histamine release
likelihood of cross reactivity between PCNs and cephalosporins
report of up to 10% overstated - true rate < 1%
which cephalosporins are assoc, with lowest rate of cross reactivity with PCNs
3rd & 4th generation
acceptable alternatives to cephalosporins with true PCN allergy
- vancomycin
- clindamycin
most common side effect of prophylactic antibiotics
pseudomembranous colitis
MOA of cephalosporins
disrupt bacterial cell wall synthesis (peptidoglycan)
MOA of vancomycin
disrupts bacteral cell wall synthesis
how often should cefazolin be redosed during surgery
Q4H
drug of choice for pts with active MRSA
vancomycin
how to reduce histamine release and hypotension with vancomycin
admin at a rate of 10-15 mg/kg over 1 h
how to minimize response to vancomycin
1 mg/kg diphenhdyramine + 4 mg/kg cimetidine 1 hr before anesthesia
antibiotics contraindicated in pregnancy
- chloramphenicol
- erythromycin
- fluoroquinolones
- tetracyclines
preferred method of skin prep before CVL placement according to the CDC
chlorohexidine
consideration for use of alcohol based products for surgical prep
flammable, allow to dry for 2 minutes
SCIP protocol
- prophylactic antibiotic admin within 60 min of incision (vanc is 120 min)
- antibiotic choice det. by surgery site
- prophylactic abx d/c’d within 24 hours postop (48 hrs for heart pts)
- glycemic control required for cardiac surgery (<200 mg/dL)
- postop wound infection dx during initial hospitalization
- surgical pts receive appropriate hair removal
- colorectal pts normothermic upon arrival to PACU ( > 36 C)
seroconversion rates after exposure to HIV-infected blood
- needle stick = 0.3%
- mucous membrane exposure = 0.09%
what is Creutzfeldt-Jakob disease
3 etiologies
prion disease that can lead to encephalopathy and dementia
- consuming contaminated animal protein
- contaminated implants (corneal or dural tissue)
- cadaveric pituitary hormone supplementation
precautions for Creutzfeld-Jakob disease
standard
main target of mycobacterium tuberculosis
anterior apical lung segments
s/s tuberculosis
- productive cough
- hemoptysis
- weight loss
- fever
- night sweats
- anorexia
- general malaise
positive TB skin test result
site of induration > 10 mm (>5 mm if pt is immunocompromised)
positive findings on CXR of TB pt
apical infiltrates and nodules
if a skin TB test is positive but a CXR is negative, is TB ruled out?
yes
first line agent for TB treatment
what are its side effects?
- isoniazid
- peripheral neuropathy, hepatotoxicity
what med can be added with isoniazid to reduce incidence of liver damage
pyridoxine
adverse effects of rifampin
- thrombocytopenia
- leukopenia
- anemia
- kidney failure
- orange urine/sweat/tears
procedure with the highest risk of skin test conversion in healthcare personnel
2nd highest?
bronchoscopy
2 - intubation
safety measures for pts with TB
- providers and staff wear N95
- HEPA filter placed between y-piece and airway
- bacterial filter on expiratory limb of circuit
- dedicated anesthesia machine and ventilator ideal
- pre and postop care in negative pressure isolation room
how long should elective procedures be delayed in pts with TB?
- pt on antituberculosis chemo
- 3 negative acid-fast bacillus tests
- demonstrates symptom improvement
most abundant WBC
what is its purpose
neutrophils
immune defense (bacterial and fungal)
granulocyte that is an essential component of allergic reactions
basophils
what is released by basophils in an allergic reaction
- leukotrienes
- histamine
- prostaglandins
how does epinephrine help in an allergic reaction?
prevents degranulation (release of intracellular contents) by binding to beta 2 receptors on cell membrane
granulocytes that defend against parasites
eosinophils
purpose of monocytes
fight bacterial, viral, and fungal infection (phagocytosis)
function of B-lymphocytes
humoral immunity (produce antibodies)
function of T-lymphocytes
cell-mediated immunity (does not produce antibodies)
function of natural killer cells
meds that reduce their function
limit spread of tumor and microbial cells
opioids reduce function (concern of cancer recurrence)
which agranulocyte releases cytokines
monocytes
anaphylaxis is an example of which type of hypersensitivity reaction?
type 1
ABO incompatibility is an example of which type of hypersensitivity reaction?
type 2
serum sickness after a snake bite is an example of which type of hypersensitivity reaction?
type 3
graft vs host reaction is an example of which type of hypersensitivity reaction?
type 4
what is the difference in an anaphylactic and an anaphylactoid reaction?
anaphylaxis requires prior sensitization or cross-reactivity
no prior exposure needed for anaphylactoid reactions
effects of H1 receptor activation
- vasodilation
- increased vascular permeability
- smooth muscle contraction (not vascular)
effects of H2 receptor activation
- tachycardia
- gastric acid secretion
metabolites of arachidonic acid
what are the effects of release
- leukotrienes
- prostaglandins
bronchoconstriction and vasodilation
CV effects of hypersensitivity reactions
- hypotension
- tachycardia
- arrythmia
- cardiac arrest
respiratory symptoms of hypersensitivity reaction
- bronchospasm
decreased ETCO2
decreased SaO2
increased PIP - laryngeal edema
- increased mucous production
GI effects of hypersensitivity reactions
- abdominal cramping
- N/V/D
what causes a type 1 hypersensitivity reaction
antigen + antibody interaction in a patient who has previously been sensitized to the agent
which hypersensitivity reaction is IgE-mediated
type 1
which hypersensitivity reaction is an immediate reaction
type 1
extrinsic asthma is an example of what type of hypersensitivity reaction
type 1
what is the best lab test to determine if an allergic response has occured?
tryptase (released from mast cells during an allergic reaction)
which type of hypersensitivity reaction is antibody-mediated
type 2
antibodies involved in type 2 hypersensitivity reaction
IgG & IgM
what causes a type 3 hypersensitivity reaction
immune complex is formed and deposited into the patient’s tissue (normally cleared from body)
which types of hypersensitivity reactions activate the complement cascade
type 2 & 3
how long is an allergic reaction delayed in a type 4 hypersensitivity reaction
at least 12 hours after exposure
dose of epi for intraoperative anaphylaxis
5-10 mcg IV for hypotension
0.1-1 mg IV for CV collapse
histamine antagonists that should be given during intraoperative anaphylaxis
- H1 blocker: diphenhydramine 0.5-1 mg/kg
- H2 blocker: ranitidine 50 mg Iv or famotidine 20 mg IV
dose and use of hydrocortisone in intraoperative anaphyalxis
250 mg IV - prevents delayed release of inflammatory compounds (no immediate effect)
med to use for refractory hypotension in intraoperative anaphylaxis
vasopressin - start at 0.01 unit/min
3 ways epinephrine treats anaphylaxis
- prevents degranulation
- CV support
- airway dilation
top 3 most common causes of perioperative anaphylaxis
- NMBs (succs most common)
- latex
- antibiotics (beta lactams most common)
groups at high risk for latex reaction
- spina bifida/myelomeningocele
- atopy
- health care workers
- allergy to banana, kiwi, mango, papaya, pineapple, tomato
side effects of cisplatin
acoustic nerve injury
nephrotoxicity
side effects of vincristine and vinblastine
peripheral neuropathy
side effects and anesthesia implications of bleomycin
pulmonary fibrosis
keep FiO2 < 30%
main adverse effect of doxorubicin
cardiotoxicity
most chemotherapeutic agents cause bone marrow suppression and thrombocytopenia. which is a key exception?
bleomycin
5 key hormones that regulate digestive activity
- gastrin
- secretin
- cholecystokinin
- gastric inhibitory peptide
- somatostatin
function of gastrin
where is it produced
- increased gastric acid secretion when food enters stomach
- increased pepsinogen secretion (converts to pepsin and aids in protein digestion)
produced in G cells of stomach
function of secretin
where is it produced
- pancreatic bicarbonate secretion
- decreased gastrin secretion
- liver secretes bile
produced in S cells of small intestine
function of cholecystokinin
where is it produced
- gallbladder contraction
- increased pancreatic enzyme secretion
produced in I cells of small intestine
function of gastric inhibitory peptide
where is it produced
- increased insulin reelase
- slows gastric emptying
- decreased gastric motility
K cells of small intestine
hormone that is the universal “off” switch for digestion (decreases all GI function)
somatostatin
where is somatostatin produced
D cells in pancreatic islet, stomach, small intestine
digestive hormone increased in Zolliger-Ellison syndrome
gastrin
digestive enzyme that causes gallbladder pain after a fatty meal
cholecystokinin
digestive enzyme that is the treatment for carcinoid tumors
somatostatin
what determines the likelihood of gastroesophageal reflux
barrier pressure
increased barrier pressure = decreased likelihood of reflux
3 things that reduce gastric barrier pressure
- anticholinergics (dec. LES tone)
- cricoid pressure ( dec. LES tone)
- pregnancy (dec. LES tone and inc. intragastric pressure)
what drug increases gastric barrier pressure
metoclopramide (inc. LES tone)
does succs affect gastric barrier pressure?
no - increased LES tone + increased intragastric pressure = 0 net change
gastric barrier pressure =
LES pressure - intragastric pressure
where does ondansetron antagonize serotonin receptors?
- chemoreceptor trigger zone
- peripheral receptors in GI tract and vagus nerve
where is the vomiting center located
nucleus tractus solitarus (medulla)
where does sensory input to the vomiting center arise from?
chemoreceptor trigger zone, GI tract, and vestibular system
receptors in the CTZ
- serotonin (5HT3)
- substance P (NK-1)
- dopamine
- opioid
5-HT3 antagonists used as antiemetics & their normal doses
- ondansetron: 4-8 mg
- granisetron: 1 mg
- dolasetron: 12.5 mg
NK-1 antagonist used as an antiemetic
aprepitant
dopamine antagonists used as antiemetics & normal doses
- metoclopramide: 10-20 mg
- droperidol: 0.625-1.25 mg
- haloperidol: 0.5-2 mg
- midazolam (may antagonize dopamine receptors in CTZ)
receptors associated with the vestibular apparatus
what drugs antagonize these receptors?
histamine (H1) - diphenhydramine
acetylcholine - scopolamine
opioid receptors reside in what sensory inputs to the vomiting center
vestibular apparatus
CTZ
how does the GI tract stimulate the vomiting center?
via CN 10
antiemetics that target the GI tract
5-HT3 antagonists
NK-1 antagonist (Aprepitant)
normal Aprepitant dose
40 mg
patient risk factors for PONV
- female
- nonsmoker
- history of motion sickness
- previous PONV
- younger age (loose association)
surgical risk factors for PONV
- long duration (>1 hour)
- GYN procedures
- laparoscopy
- breast
- plastics
- peds: strabismus, orchiopexy, T&A
anesthetic risk factors for PONV
- halogenated anesthetics
- N2O > 50%
- opioids
- etomidate
- neostigmine
what explains why the CTZ is stimulated by noxious chemicals
BBB poorly developed at CTZ
most common SEs of ondansetron
- HA
- diarrhea
when should decadron be given for PONV prophylaxis?
during induction
antiemetics that are contraindicated in pts with Parkinson’s
dopamine antagonists (phenothiazines, metoclopramide) - can cause extrapyramidal symptoms
antiemetic contraindicated in bowel obstruction
metoclopramide (d/t prokinetic effect)
what causes motion-induced nausea
M1 & H1 stimulation in vestibular system of inner ear
what type of antiemetic should pts undergoing middle ear surgery receive?
agents that target vestibular system
best time to apply scopolamine?
how long does it last
> 4 hours before anesthesia induction
lasts for 72 hours
dose of propofol that produces an antiemetic effect
10-20 mg
how can midazolam reduce PONV?
decreasing dopamine activity in CTZ
how does ephedrine affect PONV?
25 mg IM may reduce by maintaining BP and cerebral perfusion
significance of P6 acupressure point
nonpharmacologic method of reducing PONV - located 3 fingerbreadths below wrist on inner forearm in between 2 tendons
when should ondansetron be admin for PONV prophylaxis?
30 min before emergence
best class of antiemetics for patients undergoing mastoidectomy
anticholinergics
transient physiologic changes after release of pneumatic tourniquet
- increased ETCO2
- increased core body temp
- decreased BP
- decreased SvO2 (SaO2 usually normal)
- metabolic acidosis
symptoms of bone cement implantation syndrome
- V/Q mismatch (increased dead space)
- right heart failure in extreme cases
- bradycardia
- dysrhythmias
- hypotension (dec. SVR)
- pHTN (inc. PVR)
- hypoxia
- cardiac arrest
surgery assoc. with highest risk of BCIS
other surgeries with high risk
hip arthroplasty
knee arthroplasty, vertebroplasty, kyphoplasty
first signs of BCIS in awake patient under regional anesthesia
- dyspnea
- AMS
first sign of BCIS in anesthetized pt
decreased ETCO2
first line treatment of BCIS
- 100% FiO2
- IV hydration
- phenylephrine for hypotension
when is fat embolization syndrome risk greatest?
within first 72 hours of long bone injury
risk factors for fat embolization syndrome
- pelvic fracture
- femoral fracture
- instrumentation of femoral medullary canal
triad of fat embolization syndrome
- respiratory insufficiency (hypoxemia, bil. CXR infiltrates, ARDS)
- neuro involvement (confusion to coma)
- petechial rash (neck, axilla, oral mucosa, conjunctiva)
treatment of fat embolization syndrome
supportive; corticosteroids may or may not improve outcomes (controversial)
pneumatic tourniquet inflation pressure for upper extremity surgery
70-90 mmHg above SBP
pneumatic tourniquet inflation pressure for lower extremity surgery
2x over SBP
why does the tourniquet for a bier block have to be inflated for at least 20 min
premature release increases risk of seizure/cardiac arrest with LAST
tourniquet inflation pressure for upper extremity bier block
250 mmHg or 100 mmHg over SBP (whichever is higher)
tourniquet inflation pressure for lower extremity bier block
350-400 mmHg
what is Samter’s triad and what are the 3 components
aspirin-exacerbated respiratory disease - can develop life threatening bronchospasm after aspirin admin
- asthma
- allergic rhinitis
- nasal polyps
effects of COX-1 inhibition
- impaired platelet function
- gastric irritation
- reduced renal blood flow
which COX enzyme is expressed during inflammation
COX-2
effects of COX-2 inhibition
- analgesia (ceiling effect)
- anti-inflammatory effects
- antipyretic effects
CV complications of NSAIDs
increased risk of HTN, MI, HF (COX-2 inhibitors > COX-1)
pulmonary complication of NSAIDs
dec. prostaglandins = leukotrienes = bronchospasm
hematologic complication of NSAIDs
platelet inhibition = increased bleeding risk
renal complication of NSAIDs
decreased prostaglandins = decreased renal blood flow (avoid in renal disease)
CNS complication of NSAIDs
tinnitus
bone related complication of NSAIDs
decreased osteoclast and osteoblast activity may impair bone healing
GI complications of NSAIDs
gastric ulceration and bleeding
NSAID drug interactions
NSAIDs displace albumin bound drugs and increase their plasma concentration (warfarin, phenytoin, valproic acid)
why have most COX-2 inhibitors been removed from the market
concerns about CV risk
max amount of time ketorolac can be taken
5 days
___ mg ketorolac = 10 mg morphine
30
MOA of aspirin
irreversibily inhibits COX-1 and COX-2
platelet inhibition lasts for the life of the platelet
suggested MOA of acetaminophen
inhibits prostaglandin synthesis (COX-3 inhibition?)
analgesia may be from activation of descending inhibitory pain pathway in spinal cord
acid base imbalance seen with aspirin toxicity
gap metabolic acidosis
max daily dose of tylenol
4g/day
6 drugs that inhibit the COX-2 pathway
- aspirin
- ibuprofen
- naproxen
- ketorolac
- diclofenac
- indomethacin
perioperative implication of licorice as an herbal supplement
may mimic Conn’s syndrome:
- mimics effects of aldosterone
- sodium and water retention with decreased K+
perioperative implications of valerian root as an herbal medication
- decreases MAC (increased GABA)
- may prolong duration of anesthetics
- abrupt discontinuation can cause withdrawal
perioperative implication of St. Jon’s Wort as an herbal medication
when should it be d/c’d before surgery?
- serotonin syndrome with MAOIs
- CYP3A4 induction
- decreased serum level of warfarin, protease inhibitors, digoxin
- may prolong anesthetic agent duration
d/c 5 days preop
perioperative implication of garlic as an herbal medication
when should it be d/c’d before surgery?
- increased bleeding risk
- decreased serum glucose
d/c 7 days preop
ephedra (Ma Huang) interactions and toxicity
- serotonin syndrome with MAOIs
- catecholamine depletion with long term use (HD instability)
- sympathomimetic effects
anesthetic implications of ginger as an herbal supplement
increased bleeding risk
anesthesia implications of ginseng as an herbal supplement
- increased bleeding risk
- enhanced SNS effects of sympathomimetics
- may cause hypoglycemia (risk in fasting patient)
anesthesia implicaitons of kava kava as an herbal supplement
- decreased MAC (increased GABA)
- may prolong duration of anesthetic agents
anesthetic implications of Saw Palmetto
increased bleeding risk
4 herbal supplements that increase the risk of bleeding
- Garlic
- Ginger
- Gingko
- Ginseng
(4 G’s)
ASA Pre-Anesthesia Checkout Procedure recommendations - tasks to complete before every patient
- verify suction
- check function of monitors and alarms
- check vaporizers filled, ports closed
- check CO2 absorbent
- high pressure leak test
- assess unidirectional valves
- document
what agency sets the standards for required components of the anesthesia machine
american society for testing and materials
agency that sets the standards for compressed gas cylinders
US department of transportation
agency that sets the standards for food and drugs
FDA
agency that created the 1993 Anesthesia Machine Pre-Use Checkout procedures
FDA
agency that sets standards for acceptable occupational exposure to volatiles
OSHA
agency that certifies hospitals that meet specific safety standards
Joint Commission (JCAHCO)
MRI zone 1
public access, requires no supercision
ex- hallway outside MRI Suite
MRI zone 2
public access + minimal supervision
ex- entrance to MRI suite
MRI safety zone 3
limited access + strict supervision
ex- MRI control room
MRI zone 4
very limited access + very strict supervision
ex- MRI scanner room
T/F - ferromagnetic objects are allowed in MRI zone 4
nope
safe metals in MRI suite
stainless steel
titanium
aluminum
copper
common side effect of IV contrast media
nausea
EKG changes that may be seen in MRI
T wave and ST segment artifacts
what indicates an MRI safe gas cylinder
silver with a color code at the top
estimated anesthetic mortality assoc. with each ASA class
1 - 0.04 per 10,000 anesthetics
2 - 0.5 per 10,000
3 - 2.7 per 10,000
4 - 5.5 per 10,000
according to closed claims analysis, what are the 4 most common causes of injury (in order) that result in claims filed?
- regional anesthesia (20%)
- respiratory events (17%)
- CV events (13%)
- equipment failure (10%)
what is the modified Aldrete scoring system
used to quantify readiness for discharge from PACU
assesses 5 things:
activiy, respiration, circulation, consciousness, O2 sat
modified Aldrete score that suggests readiness for PACU discharge
score of 9 or greater
modified Aldrete scoring system: Activity
2: moves all extremities voluntarily or on command and can lift head
1: moves 2 extremities voluntarily or on command and can lift head
0: cannot move extremities or lift head
modified Aldrete scoring system: Respirations
2: breathes normally, can cough effectively
1: dyspneic, shallow, or otherwise inadequate breathing
0: apneic
modified Aldrete scoring system: Circulation
2: BP within 20 mmHg of preanesthetic value (min SBP = 90)
1: BP within 20-50 mmHg of preanesthetic value
0: BP > 50 mmHg of preanesthetic value
modified Aldrete scoring system: Consciousness
2: fully awake
1: arousable to voice
0: unresponsive to voice but may be responsive to painful stimuli
modified Aldrete scoring system: O2 sat
2: SpO2 > 92% on RA
1: SpO2 > 90% but needs supplemental O2
0: SpO2 < 90% on supplemental O2
time to onset of sympathomimetic syndrome
up to 30 min
causes of sympathomimetic syndrome
amphetamines
cocaine
key features of sympathomimetic syndrome
- agitation
- hallucinations
- arrhythmias
- myocardial ischemia
treatment of symapthomimetic syndrome
vasodilators
labetolol
time to onset of TCA overdose
up to 6 hours
key features of TCA overdose
- hypotension
- dec. LOC/coma
- polymorphic VT
treatment of TCA overdose
magnesium
serum alkalization
time to onset of serotonin syndrome
up to 12 hours
drugs that can cause serotonin syndrome
- SSRIs
- SNRIs
- MAOIs
- ecstasy
key features of serotonin syndrome
- akathisia
- mydriasis
- tremor
- AMS
- clonus
- muscle rigidity
treatment of serotonin syndrome
cyproheptadine (5-HT2A blocker)
time to onset of anticholinergic syndrome
up to 12 hours
causes of anticholinergic syndrome
atropine
scopolamine
key features of anticholinergic syndrome
- red, hot, dry skin
- mydriasis
- delirium
time to onset of NMS
up to 24-72 hours
key features of NMS
- bradykinesia
- dec. LOC/coma
- rhabdo
- myoglobinuria
- acidosis
- ANS instability
- muscle rigidity
- normal pupils
treatment of NMS
bromocriptine
dantrolene
ECT